Edelbrock Performer aluminum head

[atmafox]

So I just got an aluminum head made by Edelbrock in, it's going to be the basis of my 258 torque build.  Figured I'd share some pictures.

Re reasons:
• Improved combustion chambers
• Improved port design for better flow
• Dual coil valve springs to eliminate valve float

Going to combine it with aluminum roller rockers to reduce loss due to drag in the valve train, plus a 2005 4.0 valve cover with the improved oil baffles.

Between all of this I hope to see significant efficiency improvements.  I'll be using Haltech EFI to build a modern coil on plug distributorless configuration.

I'll update this thread as I work through the project.  Expect long gaps between posts, but I hope to finish it by the end of next year.

[Canoe]

Sound great!

The only thing that sounds suspect is aluminum roller rockers. While they sound great, too many reports of too high wear on the rollers, and insufficient rocker arm strength/longevity. You don't want to be replacing those every year or two. Check carefully what has been proven for roller rockers on the 4.0. Not so surprising given the stresses the rocker is under, once there's enough aluminum in the rocker to take the forces involved, there's not as much difference in moving mass between the aluminum and the steel.

[vangremlin]

Wow, that's a nice looking unit!

Are you going to upgrade your cam also?  When I put a 4.0 head on mine I was given good advice to upgrade the cam as that also makes a big difference.  Good luck, looking forward to reading about your progress!

[Taylor]

Those are awesome. I haven’t even tried to talk my wife into one.
Good luck on the build and keep us informed. I like the idea of coil packs. A youtube channel called horsepower monster covered a similar 4.0 built at newcomer racing in NC.

[atmafox]

Yup, tentatively planning on a schneider solid tappet cam optimized for 1,500-5,500 RPM re the cam shaft upgrade.

This is a 258 bottom end and will be staying that way as well, because I like the idea of building a 258cu out to keep up with the best 4.0 (i.e. not stroker) builds and then some.

... now, in the meantime while I'm putting together the parts, I get to figure out what's wrong with the acceleration pump on the carter again.  Wheeeeefun.

[atmafox]

Well, plans have changed.  I'm doing a carb upgrade now -- slightly off the beaten path with a Weber 32/36 but the Jeepers use it more often.  380cfm vs (from what I could find) 195cfm for the BBD.  That'll push EFI back a bit but... the BBD's accel pump has died on me for a second time and I'm really tired of dealing with that.  Makes her next to undrivable.

[Canoe]

Careful with that.
Early BBD was 195 CFM, the number one sees thrown around the most.
Best I've be able to find out, the stock Eagle 4.2 BBD was 285 CFM.

I chose my MC2150 1.08 thinking its 287 CFM was an upgrade, but it was ~= to the 285 CFM BBD it replaced. This was for an upgrade to the 4.0 7120 head, so a higher CFM carb could have been used.

You may want to do the math for the CFM of your engine & head at your top RPM, to ensure that the carb can provide that. If my math is correct, for a stock 258 @5,000 rpm, the CFM is 373 CFM. (And you may not reliably get 5,000 rpm with the stock valve springs.) So a 380 CFM looks good for stock 4.2 engine (and it's questionable that the stock head can deliver that flow to the cylinders; with the stock head you'll likely not see the performance expected from 380 CFM). That explains why that carb would be often used by Jeepers.

If you're going to go for a better head at some point, say one that will allow a higher RPM, you may want to pick a carb that provides what that CFM potential/requirement will be. The 380 CFM carb may already be your best choice.

[atmafox]

Thanks!  My gut told me that but I didn't work the math out.  That said, come time to put the aluminum head on I'm going to go EFI.  So that will wait longer too, but such is life.

[Canoe]

If you're going to be running a stock 4.2 with just an upgraded carb, here's alternate carbs that may save you money, depending on the source, rebuild, etc..

The guys who rebuilt my 4.2 said that having too large a carb is a mistake. I don't know what "too large" is defined as.

For a 4.2 block:
* @5,000 rpm, 373 cfm
* @5,600 rpm, 418 cfm
* @6,000 rpm, 448 cfm

Basically, if the 4.2 doesn't have the upgrades that let it reach its potential (head, headers, cam), something around 285 cfm is believed to be the limit for a stock 4.2.

One Jeep person was recommending the 2150 over the 2100, due to having required vac hookups. Here's what he summarized when he researched which 2150 was being used with good results on Jeep 4.2 engines.

* Stock 4.2 - MC2150 with 1.08 Venturi (287 cfm) and 46-48 Jets depending on elevation.
* Fully Rebuilt 4.2 - 4.0HO Head, Cam, Intake, Headers - MC 2150 with 1.21 Venturi (351 cfm) and 50-56 jets depending on elevation.

But the 2100 also has
* 1.23 venturi 356 cfm
* 1.33 venturi 424 cfm
* 1.33 venturi 450 cfm with 108 stamping

So the Jeepers using the 380 cfm carb may have various upgrades over a stock 4.2. Without those (head, headers?, cam?), 380 cfm may be too large; may be wasting gas and/or not running well. Perhaps you should confirm if that 380 cfm carb is getting used with good results on a stock 4.2, and with what jet sizes. Get the same for the larger MC2100's?

[atmafox]

Part of the equation is I can buy a new, genuine Weber 32/36.  Already have, actually.  When I looked for MC2100s, I kept finding 'new' instances that primarily appear to be Chinese knockoffs.  Plus, I'm not sure if the adapter plates are still available.

I'll be sure to let everyone know how the Weber 32/36 performs.  I know the stock 2" exhaust is a limiting factor too(that's going to be upgraded when I do the EFI build, don't worry =).  On the other hand, in the communities I come from, this carb model is often used on Toyota 3A and 4A motors which are sub-2L.  Those are definitely cases where it's too much carb for the motor.

Finally, well, there aren't many smaller new carbs available these days.  I'd have gone with a smaller Weber if I could get one new, assuming the adapters and docco was there to make it relatively drop in.  I'm also lucky in that I have a 1980 with very simple vacuum; they line up pretty much one to one with what's on the carb.

Thank you again for all the advice!
-Atma

P.S. Of interest is that the wife (also a gearhead!  I'm truly blessed) wanted to design an adapter plate to install an Aisin 2-barrel off of a 22R on the 258.  Magnificent little carb pushing about 383cfm (so right in line with the Weber 32/36) and we have a spare sitting around.  Adapter plate design and manufacture though would take longer than I want to wait, not to mention figuring out linkages and such.  It'd have been hilarious, but alas, it is not to be.

[Canoe]

Part of the equation is I can buy a new, genuine Weber 32/36.  Already have, actually.  When I looked for MC2100s, I kept finding 'new' instances that primarily appear to be Chinese knockoffs.  ...

I wish I could buy a new one. I got new MC2150, expecting the altitude comp on it. Nope - knockoff. At least mine runs well, compared to others.

... P.S. Of interest is that the wife (also a gearhead!  I'm truly blessed) wanted to design an adapter plate to install an Aisin 2-barrel off of a 22R on the 258.  Magnificent little carb pushing about 383cfm (so right in line with the Weber 32/36) and we have a spare sitting around.  Adapter plate design and manufacture though would take longer than I want to wait, not to mention figuring out linkages and such.  It'd have been hilarious, but alas, it is not to be.

Now that is very interesting. They should also have a suitable air filter housing. A quick look at ebay, makes me fear we'd be looking at the same knockoff issue. Claiming for years ranging from 1981 - 1995. There's enough Jeepers using the 22r/22re that off-road mods on 258 engines are known too.

A quick working prototype for an adapter plate can be made out of maple. Harder maple is better, but harder to work. As rough or as finished as you'd care to put the work in. Super easy to drill, rasp, then file the hole sides to slope to match openings for the least turbulent flow. Super smooth sides have more drag; some texture means it retains a thicker boundary layer which has significantly less drag. Once that is done to your acceptance:
* de-grease the carb mount and the carb
* torque the carb & adapter (to carb mount spec) in place, let sit for ten to twenty minutes, then disassemble
* (Optional: now seal the maple by rubbing in something to seal it with; examples: tung oil, epoxy glue, JB-Weld diluted with lacquer thinner or acetone. Don't seal the exposed sides that will have fuel/air vapour flowing through it, unless its with something you know will not dissolve.)
* Cut some gasket material for both sides of the adapter, use some gasket tack and then reassemble.
Figuring out a throttle linkage should be straight forward. If auto-trans, you need to keep the linkage for the trans valve in play.